Solvent absorption processes for separating components of an impure feed gas are disclosed. The processes involve two stages of gas purification. The acid gases including hydrogen sulfide, carbon dioxide and other sulfur compounds are simultaneously removed from the feed gas by contact with a physical solvent in two stages. The subject matter disclosed provides improved processes to reduce the operating costs of the system.

Waste gas mixtures produced and used in industry may contain harmful sulphurous compounds. The present disclosure provides a method for treatment of gas mixtures contaminated with harmful sulphurous compounds by using microorganisms capable of degrading said harmful sulphurous compounds which involves controlling nitrate levels in the medium in which microbiological conversion of harmful sulphurous compounds takes place at high levels.

A method is provided in which a carbon dioxide containing flue gas is provided by combusting a carbonaceous fuel in a high pressure steam generating unit using combustion air, and in which the carbon dioxide in the flue gas is at least partially captured and compressed in a carbon dioxide capture and compression unit having a carbon dioxide scrubber operated with an absorbing liquid which is regenerated using low pressure steam. The combustion air used in the high pressure steam generating unit is at least partially heated using sensible heat of the flue gas and/or the steam used for regenerating the absorption liquid of the carbon dioxide scrubber is at least partially generated using sensible heat of the flue gas. A corresponding system is also described herein.

Sorbent compositions containing calcium and iodine are added to coal to mitigate the release of mercury and/or other harmful elements into the environment during combustion of coal containing natural levels of mercury.

The methods and systems are disclosed which leverage sulfur abatement resources present at most refineries or other hydrocarbon processing plants, such as natural gas processing plants to capture and treat sulfur-containing byproducts, such as SO.sub.2, generated during the regeneration of spent HDP catalysts. Thus, the disclosed methods and systems allow for converting hazardous waste spent catalyst to a salable product at it source while simultaneously capturing the sulfur oxides removed from the catalyst and converting them to a useful product instead of a resultant waste stream requiring management and/or disposal. Thus, spent sulfur bearing refinery wastes, such as HDP catalyst, can be roasted or regenerated at the refinery site to convert the hazardous sulfur-bearing wastes into one or more salable products.

Sorbent compositions containing halogen and either nitrates or nitrites are added to coal to mitigate the release of mercury and/or other harmful elements into the environment during combustion of coal containing natural levels of mercury.

Materials which react with (scavenge) sulfur compounds, such as hydrogen sulfide and mercaptans, are useful for limiting sulfur-induced corrosion. Surface-modified particles incorporating a hexahydrotriazine moiety are disclosed and used as sulfur scavengers. These surface-modified particles are used a filter media in fixed filter systems and as additives to fluids including sulfur compounds. The hexahydrotriazine moiety can react with sulfur compounds in such a manner as to bind sulfur atoms to the surface-modified particles, thus allowing removal of the sulfur atoms from fluids such as crude oil, natural gas, hydrocarbon combustion exhaust gases, sulfur polluted air and water. The surface-modified particles may, in general, be sized to allow separation of the particles from the process fluid by sedimentation, size-exclusion filtration or the like.

Materials which react with (scavenge) sulfur compounds, such as hydrogen sulfide and mercaptans, are useful for limiting sulfur-induced corrosion. Surface-modified particles incorporating a hexahydrotriazine moiety are disclosed and used as sulfur scavengers. These surface-modified particles are used a filter media in fixed filter systems and as additives to fluids including sulfur compounds. The hexahydrotriazine moiety can react with sulfur compounds in such a manner as to bind sulfur atoms to the surface-modified particles, thus allowing removal of the sulfur atoms from fluids such as crude oil, natural gas, hydrocarbon combustion exhaust gases, sulfur polluted air and water. The surface-modified particles may, in general, be sized to allow separation of the particles from the process fluid by sedimentation, size-exclusion filtration or the like.

A system for processing a gas stream can include an acid gas removal unit comprising a first absorber unit, a compressor, and a second absorber unit. The first absorber unit is configured to receive a feed gas stream containing organic sulfur species and acid gas components, remove at least a portion of the organic sulfur species and acid gas components using a semi-rich solvent at a first pressure, produce a semi-treated gas stream, and produce a rich solvent stream. The compressor unit is configured to compress the semi-treated gas stream from the first pressure to a higher second pressure. The second absorber unit is configured to receive the compressed semi-treated gas stream, remove at least a portion of any organic sulfur species and acid gas components present in the compressed semi-treated gas stream using a lean solvent, produce the semi-rich solvent stream, and produce a treated gas stream.

A system for processing a gas stream can include an acid gas removal unit comprising a first absorber unit, a compressor, and a second absorber unit. The first absorber unit is configured to receive a feed gas stream containing organic sulfur species and acid gas components, remove at least a portion of the organic sulfur species and acid gas components using a semi-rich solvent at a first pressure, produce a semi-treated gas stream, and produce a rich solvent stream. The compressor unit is configured to compress the semi-treated gas stream from the first pressure to a higher second pressure. The second absorber unit is configured to receive the compressed semi-treated gas stream, remove at least a portion of any organic sulfur species and acid gas components present in the compressed semi-treated gas stream using a lean solvent, produce the semi-rich solvent stream, and produce a treated gas stream.